Initialize ice at small inland lakes in the northern hemisphere with 4 km Interactive Multi-sensor Snow and Ice Mapping System (IMS) ice analysis data from the National Ice Center. For large water bodies, use 5 minute NCEP/MMAB ice analysis data to replace 30 minute ice data

Replace update of model snow depth by direct insertion of AFWA depth data with a blend of the model first guess depth and the AFWA depth.

Use X-number to prepare spectral transform base functions. X-number is a numerical technique. It uses paired numbers to represent real number to avoid computational underflow or overflow that can occur in spectral truncation for wave number larger than T1000.

Update to version 2.1.3 of the Community Radiative Transfer Model (CRTM). CRTM v2.1.3 improves specification of microwave sea surface emissivities. This, in turn, improves the analysis of near surface temperature over water, especially in the southern oceans.

3) Output product changes
All filenames given below are on the NCEP ftp server, the NCEP http server, NOMADS or the NWS ftp server respectively via the following URLs (YYYYMMDD is the year, month, and day; CC is the cycle):

The packing for GRIB2 will be switched to second order complex packing. The changes will result in much faster IO time compared with the existing JPEG packing. The second order packing provides good accuracy, although files will be slightly larger than JPEG packing.

The changes involve modifying the list of stations for which BUFR data is generated for the GFS. The changes will also modify the lists of stations in the GFS BUFR sounding collectives disseminated on NOAAPORT. For the full list please reference this page:

Use of the enhanced radiance bias correction scheme will change the abias file. The format of the file is being changed to incorporate information from the satang file.

gdas.YYYYMMDD/gdas1.tCCz.abias

The GFS cyclone tracker file code has changed from "NA" to "AA" for storms in the Arabian Sea.
PT.text_GP.tratcf/cyclone.trackatcf
Change variables averaged or accumulated over time, such as precipitation accumulation, will go from 12 hourly to 6 hourly between forecast hours 180 to 240.

GFS product delivery timing on NOMADS, the ftp server and NOAAPORT will be delayed for numerous products. Pressure GRIB (*pgrb*) files will be as much as 20 minutes delayed. Please reference this page for a full list of delays:

Due to system constraints the parallel GFS will run on the backup supercomputer. This will cause impact to output availability on at least 3 days due to mandatory maintenance. We will notify users when a cycle will not be available through this user list:

https://lstsrv.ncep.noaa.gov/mailman/listinfo/ncep.list.nomads-ftpprd

Starting in late October all parallel data sets will be available on the following servers:

NCEP urges all users to ensure their decoders can handle changes in content order, changes in the scaling factor component within the product definition section (PDS) of the GRIB files, and volume changes. These elements may change with future NCEP model implementations. NCEP will make every attempt to alert users to these changes before implementation.

Previous Implementations:

Date

Title

Beginning with the 1200 Coordinated Universal Time (UTC) model run on Wednesday, September 5, 2012, the National Centers for Environmental Prediction (NCEP) Central Operations will implement a correction to the Land Surface Model used to drive the Global Forecast System (GFS). This correction is expected to improve the cool and moist bias in the near surface air temperature and moisture fields during the warm season.

Starting in mid-June 2012 NCEP was informed about a problem with the GFS near surface temperature and moisture simulations verifying in the late afternoon over the central US where drought conditions existed. Specifically, customers noted that a significant 2m cold and wet bias existed in both the MOS and GFS gridded products. Modelers at the NCEP Environmental Modeling Center (EMC) responsible for development of the GFS and scientists at the Meteorological Development Laboratory (MDL) identified the cause in late June. The problem was traced to a look-up table used in the land surface scheme that modulates evapotranspiration based on vegetation type and root zone depth. Current settings allowed for excessive transpiration and plant-extraction of soil moisture from deeper soil layers causing the lower atmospheric boundary layer to become too moist and cool.

EMC conducted a parallel test of the GFS with corrected land surface parameters starting in early June and running through late August, to determine if appropriate modifications to the LSM look-up table would provide a correction to the cold/wet bias without having an unexpected negative impact on other meteorological fields over the US and the globe. EMC conducted an assessment of the GFS parallel and found the change to the land surface model significantly reduced the cold/wet bias over the US and improved the 0-3 day precipitation forecasts. In addition, MDL conducted an objective evaluation of the GFS MOS guidance generated from the GFS parallel output. MDL concluded that the corrections in the GFS parallel output had the desired effect of reducing the cold/wet bias resulting in improved bias and error scores in the GFS MOS temperature and dewpoint guidance. Slight improvement was also noted in the GFS MOS probability of precipitation guidance generated from the GFS parallel output. A summary of MDL's evaluation and comparisons of GFS MOS text bulletins generated from the GFS parallel output can be viewed at

NCEP (and MDL) also conducted a 1.5 month GFS parallel evaluation for the period Jan-Feb 2012 to test the land surface model correction during the US cold season. As expected, analysis of results indicate that the change in the land surface model had little impact on the simulated 2m temperature and dewpoint given the low solar forcing during the winter months. MDL's analysis of the MOS guidance from the GFS parallel during the cool season sample also indicated minimal impact on the 2m temperature and dewpoint.

Based on the positive results of the GFS parallel tests and the severity of the cold and wet bias in the near surface air temperature, the NCEP Director has approved implementation of the correction to the land surface model. NCEP Central Operations plans to implement the change beginning with the 1200 UTC cycle on 5 September 2012.

We want to express or thanks to those customers who brought this problem to our attention in June. NCEP also appreciates your patience as we needed time to adequately test the GFS to ensure that correcting the land surface model did not have adverse and unexpected negative impacts on other forecast guidance (i.e., precipitation, hurricane track, hemispheric wave patterns, etc.).

Effective on or about Tuesday, May 22, 2012, beginning with the 1200 Coordinated Universal Time (UTC) run, the National Centers for Environmental Prediction (NCEP) will upgrade the GFS model and its associated data assimilation system (GDAS). The primary changes will be to the analysis system. There will be no major changes to the GFS model itself, but there will be a few modifications to the output products available from the GFS.

The primary change to the operational GFS and GDAS will be in the analysis system. The major component of the analysis change will be the incorporation of a hybrid variational/ensemble assimilation system. In this system, the background error used to project the information in the observations into the analysis is created by a combination of a static background error (as in the prior system) and a new background error produced from a lower resolution (T254) Ensemble Kalman Filter. The development of this system was done in collaboration with PSD at ESRL. The inclusion of this change and the other smaller changes listed below produce significant positive impact on forecasts in both the northern and southern hemispheres and in the tropics. In almost all measures, a positive impact is noted; however, during the summer (convective precipitation) season, a small consistent degradation of the rain/no rain line and an increase in the bias was noted. This problem will be addressed through modifications to the convective parameterization in the next global implementation.

Additional changes in this upgrade include:

Analysis Changes:

Use GPS RO bending angle rather than refractivity

Include compressibility factors for atmosphere

Retune SBUV ob errors, fix bug at top

Update radiance usage flags

Prepare for monitoring NPP and Metop-B satellite data

Add NPP ATMS satellite data

Add GOES-13/15 radiance data

Add SEVERI CSBT radiance product

Include satellite monitoring statistics code in operations

Add new satellite wind data and quality control

Update to current version of analysis trunk for optimization and preparation for future updates

GFS Model Changes:

The global spectral model is restructured, but there are no major physics or dynamics changes except for some bug fixes. The impact of these changes on the forecast is at the machine round off level.

GFS Output Product Changes:

CAPE, CIN, and Lifted Index fields will now be calculated from virtual temperature.

Users will see minor changes in simulated GOES products due to the use of the newer CRTM 2.0.2 library and coefficient files.

The following fields will be added to the 0.5, 1 and 2.5 degree pressure GRIB files

Haines index

Transport U and V

Ventilation Rate

Best 300mb Cape and CIN and their source levels

Temperature, U and V winds at 80 and 100m

Specific humidity and pressure at 80m

The Haines index will be labeled with a GRIB parameter number of 3 at this time, but with an upcoming change the GRIB parameter number will change to 2. A TIN will be issued announcing this change.

The Best 300mb CAPE and CIN are encoded in GRIB as level 255 due to a limitation in GRIB encoding.

1km helicity will be removed from the 0.5, 1 and 2.5 degree pressure GRIB files. This field was added to these files by mistake during a previous implementation.

Data Availability:

The format and content of all current GFS data sets will remain unchanged, with the exception of the addition of the new fields. GFS data are currently available on NOAAPORT, the NWS FTP server, the NCEP server and in NOMADS. The location of these data will remain unchanged. The additional new fields will be available only on the NWS and NCEP FTP servers.

Product delivery timing of the majority of GFS products is not expected to change as a result of this implementation. The GFS Downscaled Guidance (DNG) for Guam will be delayed for all forecast hours from hour 2 to 192. The delay will accumulate through the forecast hours and may be as much as 20 minutes by forecast hour 192.

More information regarding the GFS and associated products can be found at:

http://www.emc.ncep.noaa.gov/GFS/doc.php

A consistent parallel feed of data will become available on the NCEP server once the model is running in parallel on the NCEP Central Computing System by late-April. The parallel data are available via the following URLs:

http://www.ftp.ncep.noaa.gov/data/nccf/com/gfs/para

ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/gfs/para

NCEP urges all users to ensure their decoders can handle changes in content order, changes in the scaling factor component within the product definition section (PDS) of the GRIB files, changes to the GRIB Bit Map Section (BMS), and volume changes. These elements may change with future NCEP model implementations. NCEP will make every attempt to alert users to these changes before implementation.

Addition of a new membrane sea level pressure (SLP) field to the 0.5, 1.0 and 2.5 degree pressure grib (pgrb) files only. This pressure is generated by first relaxing the underground virtual temperature and then integrating the hydrostatic equation downward. The field will be subject to Spectral Gibsing near the coast, but this will be addressed in a future implementation.

The three model changes and the 192 hr precipitation change listed above are designed to address shortfalls introduced with the 27 July 2010 GFS resolution increase. The issues being addressed are:

increased low level warm bias over land

negative temperature bias in the stratosphere

negative wind speed bias in the stratosphere

error in the calculation of the 12 hr accumulated precipitation at 192 hrs only.

Data Availability:

The format and content of all GFS data sets will remain unchanged, with the exception of the addition of the new SLP field. GFS data is currently available on NOAAPORT, the NWS FTP server, the NCEP server and in NOMADS. The location of the data will remain unchanged.

Product delivery timing of the GFS products is not expected to change as a result of this implementation. More information regarding the GFS and associated products can be found at:http://www.emc.ncep.noaa.gov/GFS/doc.php

NCEP encourages all users to ensure their decoders are flexible and are able to adequately handle changes in content order, changes in the scaling factor component within the product definition section (PDS) of the GRIB files, and also any volume changes which may be forthcoming. These elements may change with future NCEP model implementations. NCEP will make every attempt to alert users to these changes prior to any implementations.

For questions regarding these changes, please contact:

John Derber

NCEP/EMC, Global Climate and Weather Modeling Branch

Camp Springs , Maryland

301-763-8000 x 7740

John.Derber@noaa.gov

John H. Ward

NCEP/EMC, Global Climate and Weather Modeling Branch

Camp Springs , Maryland

301-763-8000 x 7185

John.Ward@noaa.gov

For questions regarding the dataflow aspects of these data sets, please contact:

Model changes:

High resolution portion of forecast will be extended from 180 hrs -> 192 hrs

Significant changes in the definition of parameters in the 192 hr pressure grib (pgrb) and flux files

Also a significant change in model physics associated with this change

Additional modifications will be made to the contents of the Global Data Assimilation System (GDAS) and GFS pgrb files

Changes in model physics include:

Radiation and cloud overlap

Gravity wave grad

Hurricane relocation

New planetary boundary layer scheme

New mass flux shallow convection

Updated deep convection scheme

Positive definite tracer transport scheme

New parameter for the GFS forecast pressure grib file:

Max wind gust

Several parameters are being deleted from the GDAS analysis pressure grib files because they are not valid for the analysis dataset and have never provided pertinent information:

4 precipitation types

Convective precipitation rate

Land sea mask

Latent heat flux

Sensible heat flux

Precipitation rate

2 m RH

2 m specific humidity

2 m temperature

Boundary layer cloud cover

Low cloud cover

Convective cloud cover

Skin temperature

Surface upward long wave flux

Surface upward short wave flux helicity

These parameters are being deleted from the Global Forecast Model simulated GOES grib file because they were included in error:

Mean sea level pressure

WAVE-5 geopotential height

All accumulated or averaged values in the 192 hr pgrb and flux files will now be over a 6 hour period instead of 12 hours

The format and content of the 3 hourly files from 180 to 192 hours will be the same as the files from 0 to 180

For the flux file this includes the majority of the parameters in the files

Parameters changing in the pgrb file:

2 m above ground max. temperature

2 m above ground min. temperature

Surface albedo

Surface clear air UV-B downward solar flux

Surface categorical freezing rain

Surface categorical ice pellets

Surface convective precipitation rate

Surface categorical rain

Surface categorical snow

Atmospheric column cloud work function

Surface downward long wave flux

Surface downward short wave flux

Surface UV-B downward solar flux

Surface ground heat flux

Surface latent heat flux

Surface precipitation rate

Low cloud base pressure

Low cloud top pressure

Mid-cloud base pressure

Mid-cloud top pressure

High cloud base pressure

High cloud top pressure

Surface sensible heat flux

Atmospheric columb total cloud cover

Boundary cloud layer total cloud cover

Low cloud cover

Mid-cloud cover

High cloud cover

Low cloud top temperature

Mid-cloud top temperature

High cloud top temperature

Surface zonal gravity wave stress

Surface zonal momentum flux

Surface upward long wave flux

Top of atmosphere upward long wave flux

Surface upward short wave flux

Top of atmosphere upward short wave flux

Surface meridional gravity wave flux

Surface meridional momentum flux

Surface convective precipitation

Surface total precipitation

Surface large scale precipitation

Note: For the 192 hr pgrb products available on NOAAPORT and in AWIPS the accumulations and averages will remain over the previous 12 hour period until AWIPS is modified to accommodate this change.

One additional change to note: The file pgrbf192.grib2 on the NCEP FTP server will change from containing model output on a 2.5 degree grid to containing model output on a 1 degree grid. The 2.5 degree output will be provided in a new file with the name pgrbf192.2p5deg.grib2.

The format of the 1/2 and 1 degree pressure grib files will remain the same except for the changes in variables listed above. The size of these files will nto change significantly. With the increase in model resolution...the size of the sigma coefficient files and the surface flux files will increase significantly.